Unloading means for air-compressors.



No. 635,667. Patented Oct. 24, I899. 6. CUMMINGS.

UNLOADING MEANS FOR AIR COMPRESSORS.

(Application filed mjr 22, 1899.)

(No-Model.)

THE Nonms PETERS cn.. Pno'fournu. WASHINUYON. n. Q

' provide against waste of power in air-comdesigned for use inconnection with a double 7 NITED STATES PATENT Eric;

CHARLES CUMMINGS, OF OAKLAND, CALIFORNIA, ASSIGNOR TO THE PNEU- MATICPOWER COMPANY, OF SAN FRANCISCO, CALIFORNIA.

UNLOADING MEANS FOR AlR-COMPRESSORS.

SPECIFICATION forming part of Letters Patent No. 635,667, dated October24, 1899,.

Application filed March 22, 1899.

T0 to whom it may concern.-

Be it known that 1, CHARLES CUMMINGS, a citizen of the United States,residing at the city of Oakland, in the county of Alameda and State ofCalifornia, have invented certain new and useful Improvements inUnloading Means for Air-Compressors; and I do hereby declare that thefollowing is a full, clear, and exact description thereof.

This invention relates to certain new and useful means for unloadingair-compressors pipe or pressure system; and it consists in thearrangement of parts and details of construction, as will be hereinafterfully set forth in the drawings and described and pointed out in thespecification.

The object of the present invention is to pressors run at a constantspeed used in connection with the double=pipe system, so that in casethe use of the compressed air ceases or is cut off for the time beingthe compression or energy required to compress air during the regularworking of the compressor is obviated or dispensed with. This enables meto dispose of safety-valves or similar devices usually employed torelease the load and at the same time permits of the compressor runningunder a constant speed without doing the work of compression, thus, soto speak, allowing of the compressor-piston working idle. Ordinarily ifthe compressed air is not being utilized or consumed for a time thecompressor is still required to compress the air, and this air is forcedto escape through a safety -valve or similar device connected therewithfor this purpose. While it is true the air escapes from thehigh-pressure pipe, still certain energy has been expended in order tocompress the load, and it is this loss of energy that by the presentinvention I desire to avoid.

In carrying out my invention I take advantage of the known fact that thegreater the clearance-space in any air-compressor the less is itscapacity for compression. This being so, it follows that if theclearance-space equals in volume that portion of the compressor-cylindertraversed by the compressing-piston no compressed air would be expelledfrom the cylinder into the receivers or Serial No. 710,091. (No model.)

compressed-air pipes, provided the pressure within said receiver orair-pipes is greater than the pressure of the air in the cylinder;

hence no energy transmitted. If a clearancespace equal in volume to thatof the working portion of the compressing-cylinder is provided andconnected at each end of the said cylinder-that is, when the compressoris a double-acting oneso that by means of suitableautomatically-operated mechanism the said clearance-space may beutilized as a storage reservoir or chamber for the air taken into thecylinder at each stroke of the piston when no compressed air is beingused or needed, and, on the other hand, when the compressed air is beingused or needed, if said space is disconnected, so to speak, or closedfrom the compressor-cylinder at such times, so as to force thecompressed air into the service-pipes, it will be apparent that anair-compressor may be operated in connection with a double-pipe systemat a constant speed without loss of energy. Such idea is the basis ofthe present invention, and the foregoing object is attained by mechanismsubstantially the same as that illustrated by the accompanying sheet ofdrawings, forming a part of the present application, wherein Figure 1 isa side view in elevation of the compressor used with a double-pipesystem, illustrating the receiver and connection between the receiver,high and low pressure pipes, and between the receiver andcompressor-cylinder; and Fig. 2 is a longitudinal sectional view inelevation taken on line so 00, Fig. 1.

In the drawings the letter A is used to indicate thecompression-cylinder of an ordinary air-compressor, and A the pistonworking freely therein, said cylinder being provided with the usualair-inlet valves, through which air is drawn into the cylinder forcompression upon the stroke of the piston during the working of thedriving mechanism.

Above the compression cylinder, preferably, are arranged the connectedcylinders C C, within the upper one of which Works a piston D. Thispiston is connected by means of rods a to a similar but smaller pistonF, working freely within the cylinder C, as shown. The cylinders C and Care connected, respectively, through the medium of thehereinafter-described mechanism to the low and high pressure pipes of adouble-pipe sys tern for transmitting power. The piston D, workingfreely in cylinder 0, is acted upon by'the air contained in thelow-pressure pipe E, while the piston F, working freely in lowercylinder 0, is acted upon by the air contained in the high-pressu repipe G. Each piston being connected by rods Ct, the movement of oneimparts corresponding movement to the other.

It will be observed that the cylinder (J and piston D are considerablylarger than cylinder 0 and piston F. Infact, the areas of pistons D andF have the same ratio to each other that the pressures of air containedin the high and low pressure pipes E and G have to each other. Suchbeing the case,if the piston D has twice the area of piston F and thepressure of compressed air in the high-pressure pipe G is double that ofthe air contained in the lowpressure pipe E, then the pressure of air incylinders O and 0 will be such as to hold or maintain the pistons D andF in equilibrium when the pressures are in normal condition.

The lower end of piston D and the upper end of piston F are exposed tothe atmosphere, and the pressure from the supply or pressure pipes E andG acts upon the said pistons, preferably, through the medium of a bodyof oil located in oil-wells 1) b Each well is supplied with a removablescrew-cap c, which when removed permits of oil being fed to the wells inorder to resupply the same. Oil-well Z) is connected to cylinder G bymeans of the pipe cl, so as to supply oil under pressure to the cylinderabove or back of the piston D, while the well 19 is connected tocylinder O by pipe 61, so as to supply oil under pressure below thepiston F, Fig. 2. The oilwell I) is also connected to the low-pressuresupply E by pipe 6 and the oil-well b to the high-pressure supply G bythe pipe e, each pipe connection being supplied with a globevalve e bymeans of which the air-supply to either well may be cut off While thesame is being supplied with oil or filled.

The upper cylinder 0 is provided at its lower end with thedrip-receptacle g, which receives such oil as may escape or leak throughthe piston D, and a similar receptacle g is arranged around the upperend of cylinder 0, so as to receive such oil as escapes from the pistonF. The oil caught in drip-receptacle g escapes through outletopeningsdrilled therethrough into drip-receptacle g, and the same is drawntherefrom by means of the escape-pipe h.

In order to prevent sudden movement of the pistons D and F from oneextreme to the other of their range of action, a springf is interposedwithin the cylinder 0, so as to maintain a downward pressure upon thepiston D, Fig. 2.

The pistons D and F are connected by the rods a to the yoke I, whichyoke at its ends carries the stems II, which are provided with the adjusting-nuts 771.. These stems Z Z pass through stuffing-boxes n n andare connected to pistons H H, which pistons work freely through thechambers H H communicating with the compressing-cylinder at each. endthereof. In the Wallof these chambers H 11 are formed the ports n, whichcommunicate with the outlet-openin gs n of the chambers. When thepiston-valves H H stand in the position indicated by Fig. 2 of thedrawings, these ports are closed. At any suitable distance from thechambers 11 H are arranged the receivers or air-reservoirs J J, whichconnect, respectively, to the outlet 41 of the chambers H H by means ofthe pipe connections M M. These receivers or air-reservoirs are each ofsuch size as to have a capacity for air equal to the volume of thecompression cylinder less that occupied by the compressorpiston, or,- inother words, the volume of each receiver is equal to the air-space ofthe com pressing-cylinder with its piston. When the piston-valves H Hare raised to clear the ports a, an uninterrupted communication isestablished between the compressing-cylinder and each receiver. In orderto balance the piston valves H H, so as to equalize the air-pressurethereon, each valve is provided with a series of vertical openings orholes 19, drilled therethrough or otherwise formed.

The operation of the foregoing mechanism may be briefly and clearlydescribed in the following manner: We must presume that the high and lowpressure supply-pipes which connect the compressor with a distant motoror motors to be driven are charged with airfor instance, thelow-pressure supply-pipe at a pressure of one hundred (100) pounds andthe high-pressure supply-pipe at a pressure of two hundred (200) pounds.Now if the various parts of the apparatus stand relatively the same asillustrated by Fig. 2 of the drawings and the distant driven motorconsumes or uses the air as rapidly as it is compressed and deliveredthen the diflerence in pressure between the high and low pressuresupplypipes will remain unaltered, and the pressure upon the pistons Dand F being equal the same will be held in equilibrium. As thecompressor is presumed to be running at a constant speed, it is obviousthat if for any reason a part or the entire consumption of thecompressed air by the driven motor is cut oif the pressure in thehigh-pressure supply-pipe will increase and that of the low-pressuresupply-pipe decrease or fall, and th us destroy the fixed ratio ofpressures between the supplypipes. This variation will give a back orincreased pressure from the high-pressure pipe to the piston F throughthe described connections and a decreased pressure from the piston D tothe low-pressure supply-pipe, and thus break or destroy the equilibriumof the said pistons D and F. The moment this variance in pressures takesplace the increased pressure brought to bear against the plston F servesto raise or, force the same upward with cease? in its cylinder and carrythe piston D therewith, owing to the connecting-rods interposedtherebetween. As these pistons rise the yoke I is carried therewith, themovement of which lifts the stems Z Z and raises the piston-valves H Hwithin the chambers H H so as to partially or wholly open the ports 71and establish direct communication betweenthe compressor-cylinder andthe receivers J J, so as to permit of the air taken into the compressorto be expelled into the said receivers upon the inward and outwardstroke of the compressing-piston. Direct communicationhaving beenestablished between the compression-cylinder and the receivers and thepiston-stroke being in the direction indicated by arrow,then as thepiston moves outward the air within the cylinderin advance thereof willbe forced into receiver J, while during the movement of the piston airwill be drawn or sucked into the cylinder from the receiver J. Upon thereturn stroke of the piston the air within the cylinder will be forcedback into receiver J and air drawn or sucked into the cylinder fromreceiver J. As before stated, the volume of each receiver equaling thatof the cylinder less the space occupied by the piston it is obvious thatthe only work required of the piston at such times is only that requiredto force the air from the cylinder through an uninterrupted passage intothe respective receivers. This action will continue alternately at eachend of the compressor-cylind er so long as no compressed air is beingused. However, the moment compressed air is again required for thedriven engine the pressure in the high-pressure supply-pipe decreasesand that of the low-pressure supply-pipe increases. This gives anincreased back pressure from the low-pressure supply-pipe upon thepiston D, which forces the same downward until the said pistons D and Freach their normal position, as illustrated in Fig. 2. The downwardmovement of these pistons gives a reverse action to that of the pistonsH H, above described, lowering the same so as to close the ports n.WVhen these ports stand closed,the compressor operates in the usualmanner in connection with the high and low pressure supply-pipes, theaction of which being fully set forth and described in Letters PatentNo. 456,941,

granted me on the 4th day of August, 1891,

for an apparatus for transmitting power by means of compressed air, adetailed description of the same is not deemed necessary in the presentapplication,reference being made to the aforesaid Letters Patenttherefor.

Having thus described my invention, what I claim as new, and desire tosecure protection in by Letters Patent, is-

1. In an unloader for air-compressors, the combination with thecompressor-cylinder, of air-receivers, having approximately the samevolume as that of the cylinder, valved communications between eachreceiver and one end of the cylinder, the high and low pressuresupply-pipes, and of mechanism operated by the changed pressures in saidsupplypipes for controlling the valved communications between thecompressor-cylinder and the receivers.

2. The combination with the compressorcylinder of an air-compressor, ofthe air-re ceivers having approximately the same volume as that of thecylinder, valve-chambers arranged at each end of the cylinder andcommunicating therewith, connection between the said chambers and thereceivers, pistonvalves arranged within the chambers, the high and lowpressure supply-pipes communicate ing with the compressor cylinder, andof mechanism operated by the change of pressures within the supply-pipesfor controlling the movement of the piston-valves.

3. The combination with the compressor cylinder, of the high and lowpressure supply pipes, air-receivers of approximately the same workingvolume as the compressor-cylinder, communication between said receiversand the compressor, and of means operated by a change of pressures inthe supply-pipes for controlling the communication between thecompressor-cylinder and the air-receivers.

4. The combination with the compressorcylinder, of the valve-chamberscommunicating with the interior of the cylinder near each end thereof,the air-receivers of approxi mately the same volume as the cylinder,connection between the valve-chambers and the receivers, a piston-valveworking in each chamber so as to control the communication between thecylinder and air-receivers, the piston-cylinders, connected pistonsworking therein, a yoke carried thereby, connection between the yoke andpiston-valves, the high and lowpressure supply-pipes and the pistonswhereby the said pistons are raised and lowered by the change ofpressures in the supply-pipes.

5. The combination with the compressorcylinder, of the valve-chamberscommunicating therewith, piston-valves working therein, air-receivershaving approximately the volume of the compressor-cylinder, connectionbetween the valve-chambers and the cylinders, the piston-cylinders,pistons working therein, connection between said pistons and thepiston-Valves, oil-wells connected with each piston-cylinder, the highand low pressure supply-pipes, and of connection between said Wells andthe supply-pipes whereby the pistons are raised or lowered by the changeof pressures in the supply-pipes so as to oper ate the piston-valves inorder to control the communication between the compressor-cylinder andthe air-receivers.

In testimony whereof I hereunto affix my signature, in presence of twoWitnesses, this 11th day of March, 1899.

CHARLES CUMMINGS. Witnesses:

N. A. ACKER,

WALTER F. VANE.

